1. Field of the Invention
This invention relates generally to a method of manufacturing semiconductor devices. More specifically, this invention relates to a method of etching a metal stack. Even more specifically, this invention relates to a method of etching a metal stack having straight film stack profiles and smooth sidewalls.
2. Discussion of the Related Art
As the prices of semiconductor devices continue to plummet, more components and more complex components are incorporated into devices to extend their performance and functionally and thus to maintain their price and profitability. However, increased performance and functionality requires greater density and increased transistor counts, which in turn, requires more interconnections and increased layers to accommodate the increased number of interconnections. The interconnections connect electrodes of active devices typically formed in the active layer with other electrodes of other active devices in the active layer as well as connect active devices to terminals that communicate with external devices.
Because the number of active devices has increased dramatically and continues to increase, the number of interconnections has also increased dramatically and to accommodate the number of interconnections the number of metal layers has also has to be increased.
The increasing number of interconnections has required the interconnects to be closer together to the point that it is necessary to have smooth sidewalls to maintain desired electrical parameters between adjacent metal lines. It is necessary to have a high quality metal etch process. Some of the characteristics for a good metal etch process are as follows: straight film stack profiles, smooth sidewalls (not voidy) and a certain amount of oxide gouging to eliminate stringers and bridging. However, these results are challenging to achieve with the ever-shrinking resist film thickness. The push for smaller geometry (metal line/space/pitch) has required photolithography to decrease the photoresist thickness due to focus and exposure limitations. A problem in the metal stack etching process is the problem of achieving all the metal etch criteria without consuming all or substantially all of the layer of photoresist. Consumption of all or substantially all of the layer of photoresist prior to the completion of the etch process of the metal stack typically results in profile undercutting and voidy sidewalls of the metal stack resulting in critical dimension loss, yield loss and reliability issues.
Therefore, what is needed is a method of etching metal stacks that result in metal stacks that have straight film stack profiles, smooth sidewalls (not voidy) and a certain amount of oxide gouging to eliminate stringers and bridging.
According to the present invention, the foregoing and other objects and advantages are achieved by a method of manufacturing semiconductor devices including forming layers of materials that form a metal stack in semiconductor devices and the subsequent etching of the layers of materials utilizing etch chemistries that result in metal stacks having straight profiles and smooth sidewalls.
According to an aspect of the invention, a main etch process etches approximately 80% of the metal film, a first overetch process for a first selected period of time and a second overetch process for a second selected period of time result in the metal stacks having straight profiles and smooth sidewalls.
According to an aspect of the invention, the first overetch step includes BCl3 at about 41 sccm, Ar at about 50 sccm, Cl2 at about 34 sccm, CHF3 at about 3 sccm, a pressure of about 12 mtorr, a source power of about 1000 watts and a bias power of about 130 watts applied for a first selected period of time, which has been determined during a pre-characterization procedure.
According to another aspect of the invention, the second overetch step includes BCl3 at between 10-35 sccm, Ar between 0-50 sccm, N2 between 0-8 sccm, CHF3, between 0-8 sccm, a pressure between 10-18 mtorr, a source power of between 600-1400 watts and a bias power of between 100-2000 watts applied for a second selected period of time, which has been determined during a pre-characterization procedure.
According to another aspect of the invention, the main etch process to etch about 80% of the layer of metal film includes BCl3 at about 17 sccm, Ar at about 50 sccm, Cl2 at about 43 sccm, CHF3 at about 3 sccm, a source power of about 1000 watts and a source power of about 150 watts.
According to another aspect of the invention, the etch process to etch through the antireflection layer comprises the chemistry BCl3, Cl2, Ar, and CHF3.
According to another aspect of the invention, the etch process to etch through the hardmask layer comprises the chemistry BCl3, Ar, and CHF3.
The described method of manufacturing semiconductor devices thus provides metal stacks having straight profiles and smooth surfaces.
The present invention is better understood upon consideration of the detailed description below, in conjunction with the accompanying drawings. As will become readily apparent to those skilled in the art from the following description, there is shown and described an embodiment of this invention simply by way of illustration of the best mode to carry out the invention. As will be realized, the invention is capable of other embodiments and its several details are capable of modifications in various obvious aspects, all without departing from the scope of the invention. Accordingly, the drawings and detailed description will be regarded as illustrative in nature and not as restrictive.